Heating furnace



Sept. 8, 1925.

w. H. Fl'rcl-ll HEATING FURNAGE Fund-Feb. 14.11924 6 Sheets-She-ef 2 RH @m in N WH MMM@ U u ,W

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#INVENTGR WML/AM F/rcH W. H. FITCH HEATING FURNAGE' Filed Feb, 14. 1924 ooooooooooo oooooo-ooo o1. ooo

.Sept 8, 1925.

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Sept. s, 1925. 1,552,834 w. H. EUCH HEATING FURNACE :med vom 14, 1924 e sheets-smet 5 wmx Patented Sept. 8, 1925.

WILLIAM n. rjITcH, or ALLENIoWN, PENNSYLVANIA.

HEATING FURNACE.

Application led February 14, 1924. Serial No. 692,711.

To @ZZ whom t may concern.'

Be itknown that I, WILLIAM H. FITUH, a citizen of the United States, 'residing at Allentown, in the county of Lehigh and State of'Pennsylvania,have invented certain new and useful Improvements in Heating Furnaces; and I do hereby declarethe following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appentains to, make and use the same.

This invention relates to new and useful improvements in furnaces used in processes requiring heat treatments of materials and in' which the materials to be heated are protected from direct contactY with the flame and hot gases of combustion, if desired.

' lThe present invention is an improvement and modification of the continuous heating furnace disclosed in my prior Patent No.

4 1,388,419, issued August 23, 1921, which relates generally to a continuous heating furnace of the under-fired type in which the hot gases of combustion pass from the corn-A bustion chamber upwardly toward the arch,

, over the hearth or conveyor in intimate con- -tact with the materials to be heated, then downwardly and past the recuperator in the outlet fine and thenceI to the stack.

It is an object of the present invention to provide -a furnace of the general nature described in my above mentioned patent,

with its attendant advantages, with improvev AAments and additions whereby it may' be` utilized with l great advantage in arts and processes wherein itis impracticable to expose Athe materials to the burninggases because of oxidization', andy imperfections from' other sources.`

Itis the common present practice in the art, particularly. in the steel industry, to'

yheat .the metal for normalizing in pots or 'add orv remove material,

.I 'boxes resting upona hearth or upon a con- "tinuously or' intermittently. movable 'conf veyor. .Thismethod nis expensive and Wasteful in the labor expended, in the cost of the pots or boxes, the heat lost 1n heating the same, and the space required to position them vu n the hearth. IFurther, heat losses exist w en the gates or doors are opened to in that the cold air is admitted'to the entire'furnace.

In the present invention, a muiile or semi-munie 'is provided which extends throughout the length of the furnace, and completely covers the hearth and may beI provided; with a door or gate at either or both ends the material tobe treated. The opening of this door admits cool air only to this inner heating chamber, that is, the munie, rather ythan to the entire furnace,resulting in a very substantial saving of heat andv of time necessary for reheating the furnace to normal operating temperatures.

for the insertion and removal of The muflie, may be stacked tocapacity f With sheets, castings, enamel-waneer other` materials to be heated,resultin of heat, space and the time requlred forcompleting the processes.

Thel cost of the Inutile is more than offset by the cost of labor, pots, the heating of pots and theeconomies in fuel consumption.

The muflies may be built of materials having a high rate of heat transfer, and little sacrifice in speed of heating over the o n in a saving 4 type of hearth obtains, due to this, and `urf ther, because complete and controlled com?" bustion is obtainable, it being unnecessary to provide the usual smoky flame to prevent oxidization. y y,

A further object ofthe invention is to provide a means for controllin the velocity and distribution or propagation of the hot gasesfof combustion to the endthat a portion at least of the hotgases may be directed through the apertures in the semimuflie, into direct contact with the materials to be heated, or as an alternative the velocity may be so controlled that the gases will pass around the muiile Without substantial propagation through the apertures thereof 1n processes wherein the material to be heated should not be subjected to direct contact with the hot gases. These ends are attained by means of dampers positioned in certain of the iiues and air passage Ways described in detail hereinafter. n

When it is desired to Obtaimheat byfcon- 'vection, as well as by radiation, the muie may be modified by providing a plurality of apertures in either the arch, the side walls which heat rays and heat of convection may pass and diffuse to the heating chamber. T he walls and arch are also heated to saturation, thereby combining the advantages of heat -byradiation combustibles are deposited in the combustion chamber, the gases of combustion pass upwardly from the combustion chamber or chambers, around, over and under the muffle and hearth, completely surrounding the latter.- The velocity'of the gases is such that the remaining dust and ash carried thereby are not precipitated through the apertures of the semi-muffe to any material extent, and where the solid muiie is employed lno dust will be carried into the interior of the muiiie.

The use of a plurality of combustion chambers permits complete combustion control and a uniform distribution of heat i throughout the muiile or .heating chamber in lfurnaces of extended length.

In order to increase the eiiiciency of the fuels, the air necessary to support and control combustion is preheated by means of a 30 recuperator placed in the outlet flue of the furnace or other suitable passage way to l,the atmosphere.

In the preferred form of my invention,

, pulverized coal is the fuel employed because of its many advantages, but it is to-be uniso derstood'that the furnace may be adapted in an obvious manner for firing with liquid, .gaseous or solid fuels, without departing fromf'the spirit orscopeof the present invention. K v

Further objects and advantages, as Well as the particular nature'of the improvements, will be apparent from the description of certain preferred embodiments illustrated in the accompanying drawings, in-

which- Fig. 1 is a transverse section of my furnace along the line 1--1 of Fig. 2.

Fig. 2 isla sectional plan` view of the furnace. l e p Fig. 3 is a longitudinal section along the line 3-3 of Fig.I 2, in the direction of the arrows. f

Fig. slightly modified form of the furnace along the line 4-4 of Fig. 5, in which a plurality ofcombustion chambers and a conveyer of the car` type are employed. f c

Fig. 5 is a transverse section of the form -showninFig.4. y v

Fi is a lon 'tudinal section of a modified orm illustrating the muiiie type' furnace.

Shown in rig. e.

4 is a longitudinal section of av Fig. 7 isaitransversel section of the' form In the drawings-similar reference characters denote similar .parts throughout the several views.

The furnace is placed within a pit 10, and comprises side walls 11 and 12, end walls 13 and 14 and a top'in the form of the usual arch 15. The entire furnace is braced and held together by buck staves 16 and tie rods 17. f

The furnace may be provided' with a hearth or one of the usual ytypes of conveyers for supporting the materials to be "heated, as illustrated in the embodiments shown, and also in my priorpatent referred to previously. e

Referring particularly to Figs. 1, 2 and 3, a combustion chamber 18 is shown bound-` ed by a top wall or arch 19 and side walls 20 and 21.- The combustion chamber is separated by air spaces 22 and 23 from outlet iues or chambers 24 and 25 to be described hereinafter.

The hearth support 26 is supportedy on a plate 27 and I beams 28 extending throughout the length of the furnace and which terminate in and are supported by the end walls 13 and 14.

Supported upon the hearth support 26 and separated by air spaces from the side Walls 11 and 12 and arch 15, is a muie 29, in this form shown as a semi-muifle, which comprises side walls 30 and 31, an arch 32, and a hearth 33. i

I assageways 34-34 are provided under the hearth 33 to permit the passage of hot gases of combustion inla manner to be fully explained hereinafter. Y

The muiiie extends throughout the length of the furnace and terminates in the end walls 13 and 14, i

In certain industries it kis desirable to provide forl additional heating effects by on their inner faces as shown at 37, and

ma be operated by any suitable means',

suc as shown at 38. f' J Clean out ports 39 closed by the usual doors, are provided at suitable locations, as

shown, for the removal of precipitated nonfcombustibles.

' Referrin to Fig. 3, down-let ues 50 are 'shown in otted lines leading'1 downwardly from the upper portion Lof t e furnace to out-let flues 24 and 25 positioned on opposite sides of and in the same horizontal plane as the combustion chamber. l

These lout-let fines terminate in a common `passage way. for the products of combustion from both liues 24 and 25 to a stack-flue 52 leading to the stack 53.

The fuel which may be oil, gas, pulverized coal or other suitable substance, is admitted to the combustion chamber through a burner tube 54 extending through the wall 11. It will be understood that the fuel may be supplied to the burner tube by any suitable piping or conveyer system, depende-nt upon the nature of the fuel, and which is not illustrated as it forms no p-art of the present invention.

It is necessary to supply air to the fuel as it 'enters the combustion chamber of the furnace, in order to control combustion and to insure that complete combustion may be attained. v

The eiiiciency of combustion will be increased if the air is preheated before being applied to the furnace. Air may be taken rom any portion of the furnace where it may be exposed to the heating effect of the products of combustion, but for reasons and v objects which will appear more fully hereinafter, it is preferable to provide a recuperator system in the out-let flues 24 and 25 of the furnace.

The recuperator system is as' follows: An

"air gate 55 provided with a suitable damper 56 is supported by the elbow 57, and. may be connected to any suitable source of air pressure, not shown. The airline is directed downwardly to a T 5 in the outlet fiue 51, and is there divi ed into two ,branch systems 59 and' 60 which follow through the out-let flues 24 and 25 throughout the length of the flues, thencexthrough the walls at 61 and 62 where they .are again directed inwardly and are connected to a T 63 leading to the burner tube v54. Theex posed portions of the system are protectedV from heat losses by suitable pipe coverings 64.

The recuperators proper, may be supported or suspended within the out-let flues 24 and 25 and spaced from the walls by any suitable means which will not offer' a material obstructionto the flue gases.

The incoming air is thus preheated before reaching the burner by lfrom the furnace.

-As shown in Fig. 3, rods or pipes 65 form-l ing the core-blisters are supported centrally of the recuperators by any suitable means and serve to distribute the air along the walls of the recuperators to provide uniformly preheated air at'the burner. When pipes are used as core-busters, they are sealed at each endto cause air to flow between the outside wall and the core-buster. The air gates 55 and damper 56 serve to `by any suitable means.

the exhaust gases` control the combustion air and in some measure the velocity of the gases, but it is obvious that complete contro-l of the velocity, distribution and propagation cannot be attained by these means alone, owing yto the danger of an excess of air'in the combustion chamber. To provide for complete control, a damper 66 is shown in the out-let flue t0 the stack and whichmay be operated In larger installations, suclrfas continuous heating furnaces of high capacity, it is necessary to extend the length of the furnace,

and in order to: provide for an even distribution of heat throughout the length of the muflie, it is advisable to provide a plurality of combustion chambers. The number. of combustion chambers is obviously dependent on the length of the furnace employed and the temperature required.

Figs. 4 and 5 illustrate theA use'of a lplurality of combustion chambers in a single car type of underfred annealing furnace. Two combustion chambers 67 and 68 are shown by way of illustration, but it is to be understood, that additional combustion chambers may be provided when the site of the furnace warrants their use. Air spaces are provided at 69-69 to permit cooling of the refractory walls. v

Leading upwardly into the furnace are flues ,40 provided with upwardly diverging side walls as shown in the dotted lines 70 andr 71 in Fig. 4, to permit transverse expansion of the envelope of flame and hot 100 gases and to provide for an even distribution of heat throughout the length of the mulile. l

While it ma also be understood that any suitable heart terials to be heated may be employed, a single car 2, is shown and which travels on rails 73 in `a lower chamber 74 of the muflie 29.

A sand-seal 75 is shown at each side of the 110 car to prevent the admission of hot gases to the lower chamber 74, to protect the running gear of the conveyer. A

Suitable gates 36, provided withrefractory inserts 37 on their inner faces, close the 115 width ofbthe flues 70-71, in order that the 125.

hot gases may be .materially retarded to provide thereby for an even distribution and to prevent loss of heat.

A recuperator is shown at 82 and"com prises a system of four tubes provided ywith 130 or conveyor for the map passage ways 34, toiprovide enter the heatin core-busters, and is supported directly in the path ofthe downwardly projected gases and parallel'to the path of the waste gases in the out-let flue 80.

A damper for controlling the velocity and distribution of the gases is shown at 66 in the out-let flue 52 to the stack 53.

The members 90 merely serve as braces for the'mule and are of suchnarrow crosssection that they do not oEer a material obstruction to the passage of the hot gases.

One of the burners is indicated at 54 in Fig.v 5.

The modification shown in Figs. 6 and l7 is essentially similar to that shown in Figs. 1, 2 and 3 with this difference, a self-supporting solid wall muifle is shown at 91, consisting of the hearth 92, side walls 93 and 94and arch 95, each of which terminates in the end walls 96 and 97.

Beneath the hearth are a plurality of gas for further heating of the hearth.

A combustion chamber is sho'wn at 18 and is separated from outlet iiues 24--25 by air spaces 22 and 23.

A recuperator 59-60 out-let flue 24 and 25.

The operation of the furnace is generally as follows: y

Fuel and air are admitted in suitable quantities to the combustion chamber 18, the amount of air being regulated by the air gate 55. Owing to the peculiar arrangement of the parts of my furnace, it is unnecessary to provide the usual smoky iame to protect the materials from oxidation, and complete and controlled combustion may be maintained without danger.

The size of the combustion chamber, and itsposition beneath the heating chamber provide for substantially complete combustion of the fuel before the gases and flame chamber. For this reason, nearlyv all so id or molten non-combustibles present in the fuel when pulverized is l shown in each coal is used, are precipitated in the combustion chamber from which they may be removed at convenient intervals through the clean-out ports.

The envelope of ,flame and hot gases, as it passes upwardly through the iues, expands transversely thereinv and in the air space separating the furnace wall and mufile.

The hot gases diffuse and pass completely u over the mulile, and thence downwardly to- Y wardthe out-let'flue. The relativel small apertures, in the toprof the out-let c amber decrease the velocity of the gases and per mit a more even distribution'of heat.

` 'In the furnace shown in 1, 2, 3, y6 and 7, the gas passage ways 34 provide for additional heating of the hearth.. It

has been` observed in the operation of this furnace, that the relatively high velocity of the gases entering the heating chamber, creand providing for more efficient combustion.

In some industries it is desirable to provide for heating by convection as well as by radiation, to this end, the apertured or semi-munie is desirable as the hot gases may be directed through the apertures in the .muflie by varying the velocity of 4the gases by means of the damper 66 in the outlet flue to the stack.` The velocity of the gas is such, however, that most of the small amount of dust and ash carried into the heating chamber is drawn entirely over the muiiie. 'Ihat which may be precipitated in the heating chamber may be removed through the clean-out ports.

When a plurality of combustion chambers is employed, the same advantages are obchamber and completely surrounds the muf-, 105

fle before passing to the out-let ue containing the recuperator.

In certain of the modifications .a portion of the gases pass under the hearthand provide additional heating effects. The damper in the stack flue permits control of heat distribution. l

While certain preferred embodiments have been shown and described, it will be understood that various changes in the number of combustion chambers maybe made, that solid or semi-muiiies may be substituted in any of the forms shown, and lthat various changes in the details of construction in the proportioning of parts of the furnace and the recu erative device may be made without departlng-from the principles of the invention as defined in the appended claims.

I claim: f

1. In an underired furnace, the combination of a heating chamber, a combustion chamber situated below the -heating chamber, a flue'leading from the` combustion provided with side walls and an arch spaced' walls and arch ofsaid muHie being separated from the side walls and arch of the heating chamber by a space forming a gaspassage, a Hue connecting the combustion chamber and the heatin chamber, a down-let Hue on the opposite side of the muie, said air spaces and Hues providing a continuous passage for hot gases leading from the combustion chamber, around the muHie and through the out-let Hue.

3. In a furnace, the combination of a heating chamber, a combustionrchamber positloned beneath said heating chamber, a Hue `leading from said combustion chamber to the heating chamber, a hearth support in said heating chamber, a muHie supported on .said hearth support, said mufHe being provided With a plurality of apertures for the admission of gases into the muHle, a plural- 'ity of down-let Hues leading fromthe heating chamber and terminating in a plurality of out-let Hues, recuperators in said out-let Hues for supplying preheated air tothe com-y bustion chamber.

4. In a furnace, the combination of a com` bustion chamber, means for admitting a mixture of fuel and air to the combustion chamber, a heating chamber positioned above the combustion chamber, a hearth-support in said heating chamber, a muHle positioned in said heating chamber, -said muHie being provided with aplurality of apertures for the admission of hot gases, a gas passage way between the muHie and the hearthsupport, a Hue leading from the combustion chamber to the heating chamber, an out-let Hue and means-in said out-let Hue to control the velocity of the gases.

5. In a furnace, the combination of a heating chamber, means in said chamber for supporting a muHle, a muiiie supported on said means having side walls and an arch terminating in the end walls of the heatin chamber and spaced from the side wa s and arch, a combustion chamber below said heating chamber, a Hue having upwardly diverging side walls connecting said combustion Vchamber to said heating chamber, said yHue providing a means whereby the envelope of hot gases and Hame will 'expand transversely and be uniformly distributed over the mufHe.

6. In an underHred muHie furnace, a heating chamber, a muHlein said chamber spaced from the side walls of the heating chamber, a gate at the end of the muiiie for the admission or removal f material to be heated, a combustion h mber below the heatingchamber, a Hue aving upwardly divergl-ng side walls leading from thecom-l bustionfchamber to the heating chamber, and means providing a passagefway to the atmosphere for the waste gases of combustion..

7. In an underfiredA muHle furnace, the

combination of a heating chamber, a muHle in said heating chamber, the side walls and arch of which terminate in the endy walls of the heating chamber andv are spaced from the side walls and arch thereof, a plurality of combustion chambers positioned beneath said heating chamber, upwardly diverging Hues leading from the combustion chamber to the heating chamber, whereby the hot gases of combustion may be uniformly distributed throughout the length of the muiiie.

8. In a furnace, the combination of a heating chamber, a muHle supported in said heating chamber, a plurality of combustion chambers positioned below said' heating -chamber and separated from each other by air spaces, a plurality of Hues leading from the. combustion chamber to the heating chamber, an out-let Hue provided with apertures of lesser width than the first 7mentioned Hues for the admission of gases from the y heating chamber to said out-let Hue, a stack Hue, and a stack for receiving the gases from the out-let Hue and discharging the same to the atmosphere. 9. In a furnace, the combination with a heating chamber, means in said chamber for supporting a muiie, said muHle being spaced from the side walls and arch of the heating chamber and terminating in the end walls, the arch of the muHle being provided with a plurality of apertures for the admission of chamber, a recuperator system in said out-let Hue in the path of thewaste gases, means for admitting"l air to said recuperator system, a burner in each combustion chamber, and means for admitting fuel and air to the burners, the air .being preheated in the recuperator system.

-In testimony whereof I aHiX my signature.

' -WILLIAM H. FITCH 

